Recovery of vehicle exhaust heat otherwise expelled from a vehicle can improve the efficiency of various vehicle systems and improve fuel economy. For example, vehicle exhaust heat has been used to warm engine coolant, especially after a cold start of the engine. Furthermore, a thermoelectric generator (TEG) can be integrated into a vehicle exhaust system to produce electrical energy from a temperature differential created by the exhaust heat and a coolant. Exhaust gas flow through the TEG must be controlled to prevent the TEG temperature from rising above a predetermined critical temperature. Control of the exhaust gas flow is typically based on a temperature sensor on the heated side of the TEG. Such temperature sensors experience a lag in indicating the actual heated side temperature as they do not change rapidly enough to reflect temperature changes due to the opening and closing of the bypass valve or changes in engine output. Accordingly, to prevent unintentionally exceeding the critical temperature, control systems for the exhaust gas flow must divert exhaust gas from the TEG at a temperature further below the critical temperature than would be necessary if a sensor without lag time issues were available. The temperature differential between the TEG and the coolant is thus decreased, and the electrical power output of the TEG is reduced.